1. Field of the Invention
The invention relates to an elastic joint member with at least one set of loops, at least two bushes, which extend transversely through the set of loops, collars, which are fastened to a respective bush end in order to axially support the set of loops on the relevant bush, and an elastomeric envelope, in which the set of loops and the bush are embedded at least in part.
2. Description of the Prior Art
Elastomeric joint members of this kind are commonly used, for example in the form of joint discs, for the cardanic connection of shafts, in particular in the drive train of motor vehicles. When joint members of this kind are assembled the bushes are fastened to shaft flanges or the like by means of threaded bolts, rivets or the like which are passed through them.
DE 3942432 C1 discloses an elastic joint member in the form of a joint disc in the case of which a plurality of sets of loops are assembled in an overlapping manner to form a ring and held together by cylindrical bushes which are passed through the overlap areas of the sets of loops. The sets of loops are fixed in the axial direction by pressing a collar onto each bush end before the entire arrangement is introduced into a vulcanising mould, in which it is given its elastomeric envelope. The collars are metal rings of an L-shaped profile which are connected to the bush not only in an axially non-displaceable manner but also in a rotationally rigid manner by pressing them onto a respective bush end. In order to prevent the bushes together with the collars fastened thereto from twisting upon tightening screws which are used to assemble the joint disc and thereby the total or partial destruction of the adhesive connection between the bushes as well as the sets of loops wrapping around them and the surrounding rubber, the bushes have at each end at least one sharp-edged projection which is hard enough to press into an associated shaft flange or the like when the associated fastening screw is tightened.
DE 19742361 A1 discloses elastic joint members which likewise comprise at least one set of loops as well as bushes which are provided with collars, in which case the sets of loops can likewise be assembled to form a self-contained ring. However here the bushes are formed as collar bushes with a respective bush part and a respective first collar, which is formed integrally onto the latter, as well as a locking arrangement at the end of the bush part which is remote from the first collar. Together with this locking arrangement, a complementary locking arrangement at a second collar forms a snap connection which is fixed axially and rotationally. The two collars have axially parallel holes into which the elastomeric envelope penetrates during vulcanisation, so that the collars, and with them also the bush parts, are firmly anchored.
The problem underlying the invention is that, in a statistically relevant number of cases, shaft trains which incorporate one or a plurality of elastic joint member(s) of the described type exhibit hitherto inexplicable deviations from the expected rotational vibration behaviour and also fail to attain their service life normally to be expected in spite of the measures initially described. The invention is based on the recognition that deviations of this kind can arise due to the occurrence when fitting joint members according to the invention in a shaft train of twisting of individual or all of the bushes and the associated collars which is slight and therefore hitherto considered irrelevant causing one or the other set of loops enveloped with rubber to be prestressed in an unplanned manner and the elastic joint member concerned consequently being unevenly loaded during operation.
The object of the invention is therefore to create conditions, through the very formation of an elastic joint member, to prevent stress accumulations in the joint member which are inconvenient during operation without the care taken when fitting the joint member having to meet unrealistically high requirements.